Tony Blair yesterday returned from the United States to face a growing backlash from Labour MPs over his stance on Lebanon.

On another day of heavy fighting as Israel pressed forward its military offensive, senior backbenchers warned that the party was in "despair" over the Prime Minister's refusal to back international c alls for an immediate ceasefire.

Critics said the anger could spill over into the party conference in September and ultimately affect the timing of his departure from Downing Street.

They urged him to distance himself from US President George Bush's support for the continued Israeli assault. Despite calling for a "complete renaissance" of Middle East strategy, with a renewed effort to establish a Palestine state, Mr Blair has resisted all calls to condemn the Israeli action.

Former Minister Joan Ruddock said there was now a sense of "despair" within the Labour ranks.

"I have not met any member of the Labour Party myself who actually agrees with our strategy," she said.

"I really can't envisage at the moment how the party conference will go.

"There is enormous anger, disappointment and the sense that there has to be a change of direction, but that the damage has been done.

"There will be a huge effort required in order to rebuild any kind of confidence and at the moment I can't see how that will be done.

"I think there is a huge legacy from Iraq and that, unfortunately, this latest problem with Israel and Lebanon will only build on that and deepen the sense that we have got a foreign policy in the Labour Party unacceptable to our membership."

Labour backbencher Dai Havard, a member of the Commons Defence Committee, was even more outspoken.

In a scathing letter to the Prime Minister, he urged him to stand up for what was "morally, politically and strategically right" rather than simply follow American policies.

"The misdirected obsession with continuing to publicly mouth the same policy as the Bush Administration in order to convince yourself and others that this gives you the ability to influence and ameliorate its actions is a deluded pretence which we all need you to abandon," he wrote.

He added pointedly: "These issues are the most urgent task that will doubtless influence your departure as Prime Minister and Labour Party leader."

The chairman of the Parliamentary Labour Party, Ann Clwyd, drew back from criticising Mr Blair directly but warned that feelings among backbenchers were running high.

"Before the recess, in the run-up to the end of our session, a lot of people were very angry," she said.

"I think the vast majority of them felt that there should be a ceasefire and the vast majority of them are very critical of Israeli policy."

The latest criticisms came against a background of reported unease within the Cabinet over the Govern-ment's position, with Leader of the Commons Jack Straw, Environment Secretary David Miliband and International Development Secretary Hilary Benn all reported to have concerns.

Even Foreign Secretary Margaret Beckett is reported to have despatched officials to press No 10 - unsuccessfully - for a change of direction.

The British deputy secretary general of the UN, Mark Malloch Brown, urged Mr Blair and Mr Bush to take a back seat in talks.

"It's not helpful for it again to appear to be the team that led on Iraq.

"This cannot be perceived as a US-UK deal with Israel," he said.

Mr Blair, who arrived this morning, was said to have been holding meetings to discuss the crisis.

"He is going to continue speaking to foreign leaders tomorrow," a spokeswoman said.